Automatic brake adjusting mechanism



Nov. 17, 1942.

F. HELL AUTOMATIC BRAKE ADJUSTING MECHANISM Filed Nov. 13, 1940 Patented Nov. 17, 1942 UNITED STATES PATENT? oer-ice AUTOMATIC BRAKE ADJUSTING MECHANISM Fritz Hell, Vienna, Germany;'vested in the Alien Property Custodian Application November 13, 1940, Serial No. 365,492

, In Germany September 30,1939

7 Claims. (01. 188'79.'5)

This invention relates to brake adjusters and shoes provided with the brake lining H and pivis particularly directed to an automatic adjusting oted at 2. 3 is the brake cylinder which houses mechanism for hydraulic'or pneumatic brakes." the pistons or pressure members 4, by means of One object of the invention is to provide a which the brake shoes are actuated and forced perfectly automatic braking mechanism in which into engagement with the brake drum 29 (shown the wear take-up is effected in infinitesimal inin Fig. 2), while 5 is a retracting spring adapted crements and ma uniformly progressing way. to return the brake shoes'to their original posi- A further object of the invention is to construct tion at the end ofeach actuation. Pivotally an adjusting mechanism of this kind which can mounted on the back plate as indicated at 1 are be operated with every assurance of safety and the adjusting eccentrics 8, having the shape of reliability and without the use of springs or simitwo-armed levers, andjof which the shorter arms lar easily braking parts. In the latter respect 8 cooperate with the drivers 6 mounted on the particular care has been taken to devise a conbrake shoes. The free ends of the longer arms struction in which no spring operated friction 8" of the levers are formed with a rising edge 9 means are employed toprevent the backward 5 of spiral-like or similar formation for cooperation movement of the adjusting elements, as it is well with the stops it] likewise mounted on the brake known that means of that type will block the shoes.

backward movement only after the back-lash has The device functions s ws! When t been taken up, and for that reason make accurate br ke lining I I s ew, t at s to say, prior t0 y adjustment impossible. wear of the friction faces, the clearance distance Still another object of the invention is the procorres to the distance between the driver vision of an adjusting mechanism which can be 6 and the opp e dge of the lever arm 8', so assembled from only a small number of elements, that no adjusting of the lever occurs when the and being of simple form will be susceptible of brake is actuated. But, when the brake shoe is incorporation at low cost and without'material orced against the drum after there has been difficulty in any conventional brake mechanism. some Wea o the brake ing the len o t e Other objects and advantages of theinvention p o the driver 5 w be ease for an will become apparent as the description of the u corresponding o the tof Wear f same proceeds, and the invention i11 b b t the friction faces, for which reason the free end understood from the consideration of the followof the lever arm W111 likewise be displaced-for ing detailed description taken in connection with T the same additional amount,while the eccentric the accompanying drawing forming a part of the 8 Will Simultaneously e rotated through an angle specification and in which similar reference nurr spon in o he mo n f i pl ement of merals indicate like parts in the difierent figures, the arm 8. When the eccentric 8 is being rowith the understanding, however, that the inventated its second arm 8", provided at its free end tion is not confined to any strict conformity with IWi'th' the rising edge 9 0f sp formation, the showing of the drawing but may be changed Will' be rotated as W reducing in this W y the or modified so long as such'changes or modificapossible distance of retraction of the brake shoe tions mark no material departure from the salif r an am u corresponding to t am u t of ent'features of the invention as expressed in th 40 wear of the brake lining to'the normal clearance appending claims. distance. It is obvious, therefore, that the clear- In the'drawing: ance-distance as well as the braking distance will Fig. 1 is a diagrammatical illustration of a em innch n e re ardle s of the amount of complete adjusting mechanism; wear which ma have taken place in the brake Fig. 2is a' sectional view of a'preferredembodi- 5 lining; O Course e retracting sp 5 Will y ment of the invention, showing th right id of to return the adjusting eccentric 8 to its original the adjusting mechanism afterremoval of the position. This, however, will be preven e by the back plate; self-locking construction of the eccentric 8 which Fig 3 is a detail sectional vie of th back makes backward rotation impossible. Such selfplate and the adjusting eccentric on line III-III oo effect ca be obta ned in Va u y of Fig, 2; particularly however through adequate selection Fig. 4 is a detail view of a simple mechanism of the ratio of the two leverarms 8' and 8". If indicating the degree of wear of the brake lining. the ratio of the two lever arms is large enough Referring now to the drawing in detail, the the curve 9 will become so flat that self-locking reference numeral l (in Fig. 1) denotes the brake '55 W111 result, and such self-locking action can be further augmented by friction created with the aid of springs or otherwise between the lever and the underlying back plate.

In the modified form of construction illustrated in Fig. 2 the adjusting eccentric 8 is not actuated directly by the driver 6 but through the.

medium of the forked end lever l2, which latter is pivotally mounted On the back plate, as indicated at l3. The shorter arm I4 of the lever l2 cooperates with the driver 6, while the longer arm I 5 of that lever is formed with a slot in which is disposed a pin I! carried by the shorter arm 8' of the eccentric B. through an arrangement like this a powerful leverage may be created between the driver 6 and the lever arm 8" provided with the rising edge 9. It is further obvious that instead of the lever system suitable gear means may be employed. In the form of construction suggested in Fig. 2 the setting movement is doubled already in the area between the driver 6 and the pin l1, whereupon the ratio of the lever arms 8 and'8" further increases th setting movement to about four times the movement of the driver 6. The latter fact becomes clearly discernible whenathe starting position (shown by full lines) of the driver 6 and the lever arm I 4, on one hand, and the stop in and rising edge 9, on the other hand, is compared with the position of greatest wear A of the brake lining of the same elements (shown in dot-and-dash line position). In a construction like this the inclination of the edge 9 is a very slight one. Attention is further invited to the fact that the stop 10 has been arranged on the brake shoe at a place whose distance from the pivot 2 approxi mately corresponds to the distance of the pivot T from the pivot 2, so that the backward movement of the stop H3 caused by the retracting force of the spring 5 is always efiective in radial direction toward the pivot 1. If the lever system is devised like this it will be impossible for the stop ID, when the latter is moving backward, to return the lever 8 to its former position either by sliding along the edge 9 or in any other way, so that self-locking is already guaranteed by this construction. However, if further assurance in this respect is considered necessary the friction between the eccentric 8 and the back plate can be increased as indicated in Fig. 3. In this latter form of construction a screw I has been substituted for the pivot l. The screw 1 is an chored with its head 22 in a recess of the back plate 20 and provided at its opposite end with a nut 23, while a spring 2| mounted on the shaft of the screw bears against the nut 23 and forces the eccentric 8 against the back plate 20.

It is further possible to equip the adjusting eccentric 8 witha simple device by which the degree of wear of the brake lining will be accurately indicated, so that it can be read 01f and controled at any moment of the operation of the mechanism. For this purpose it is merely necessary to fasten to a pin 24 of the eccentric 8 (Fig. 3) one end of a Bowden-draw-member 25 Whose other end is connected to an arm 26 of a recording mechanism provided with a pointer 21 It is apparent that and an arcuate scale member 28 indicating the degree of wear of the brake lining (see Fig. 4). With the aid of a simple apparatus of this type even the slightest change in the position of the lever arm 8" will immediately be indicated by the pointer, which according to the degree of wear of the brake lining will gradually move from 0 to the nd of the scale, demonstrating in this very impressive way the necessity of an urgent renewal of the brake lining.

. A brake adjusting mechanism as described in .the present invention functions in a perfectly automatic and uniformly progressing way, the Wear take-up being accomplished in infinitesimal increments. Moreover, a device like this can be operated with every assurance of safety and reliability, as its self-locking quality is the direct result of the particular construction of the adjusting eccentric, and not dependent upon friction caused by easily braking springs.

What I claim is:

1. A wear compensating arrangement for breaks having a pivotally supported brake shoe operable against the action of resilient retracting means, said arrangement comprising a piv-v otally mounted lever having two arms of different length, a cam element arranged for actuation by the longer arm of said lever and having a rising edge, a first stop on said brake shoe for cooperation with the shorter arm of said lever, and a second stop on said brake shoe for cooperation with said rising edge of said cam element to effect a wear compensating adjustment of the brake shoe when said lever is rotated upon engagement of its shorter arm by said first stop.

2. An arrangement, as claimed in claim 1, in which the inclination of said rising edge of said cam element is so slight that pressure exercised by said second stop against said rising edge owing to the pulling force exerted upon said brake shoe by said retracting means is unable to effect a backward rotation of said lever and cam.

3. An arrangement, as claimed in claim 1, in which said second stop is arranged about halfway between the pivoted end and the free end of said brake shoe.

4. An arrangement as claimed in claim 1, in which said lever and cam element are so dimensioned and arranged that any linear movement of said first stop which serves to actuate said lever results in a greater linear movement of said rising edge on said cam element.

5. Anarrangement, as claimed in claim 1, in which said cam element is integral with the longer arm of said lever.

6. An arrangement, as claimed inclaim 1, in which the distance between said second stop and the pivot point of the brake shoe is substantially equal to the distance between the pivot point of said cam element and the pivot point of said brake shoe.

7. An arrangement, as claimed in claim 1, in which said cam element is formed as a separate lever to increase the ratio of leverage between said first stop and said rising edge.

FRITZ HELL. 

